Preparation of Frémy's salt (potassium nitrosodisulphonate) by electro-chemical oxidation of potassium hydroxylamine disulphonate

Abstract

Oxidation of alkaline solutions of potassium hydroxylamine disulphonate at platinum, nickel, or carbon anodes in a divided cell with an applied potential of ca. 3V produces Frémy's salt in nearly quantitative yield and with very high current efficiency. Nitrite ion, a common impurity in hydroxylamine disulphonate prepared by conventional methods, and a cause of instability in Frémy's salt, is preferentially oxidised to nitrate. Attention is drawn to a convenient method for preparing hydroxylamine disulphonate free from nitrite.